NEW YORK — The Federal Trade Commission is suing Amazon over charges that the company has not done enough to prevent children from making unauthorized in-app purchases, according to a complaint filed Thursday in federal court.

The move had been expected since last week, when Amazon said it wouldn't settle with the FTC over the charges. Amazon said in a letter to the FTC last week that it had already refunded money to parents who complained and was prepared to go to court.

On Thursday Amazon said its statements in the letter still apply and did not comment further.